The present disclosure relates to a self-actuated bleed valve for assisting start-up of a gas turbine engine.
Gas turbine engines are provided with a number of functional sections, including a fan section, a compressor section, a combustion section, and a turbine section. Air and fuel are combusted in the combustion section. The products of the combustion section move downstream, and pass over a series of turbine rotors in the turbine section, thereby driving the turbine rotors to provide power. The turbine rotors in the turbine section drive the compressor section and the fan section.
At start-up, the turbine section of the gas turbine engine takes time to fully provide power to the compressor section and fan section. Thus, driving the compressor section at start-up is more challenging for the turbine section than at steady state conditions. Prior art gas turbine engines generally include a bleed valve to bleed air away from the compressor section during start-up to reduce the load the turbine section experiences from the compressor section. The valve is open at start-up and moved to a closed position after start-up has been completed.
The actuation of many prior art bleed valves is controlled with external active control mechanisms, such as solenoids. The actuation of some prior art bleed valves is controlled passively and mechanically by a spring that biases a piston open. In these passively controlled bleed valves, the piston closes when the total gage pressure of the flow upstream of the piston exceeds the biasing force of the spring. A passively controlled bleed valve that relies on the total upstream gage pressure of the flow for control may be exposed to particles and contamination ingested by the gas turbine engine.